Upendra Behera

DEVELOPMENT OF CRYOGENIC LOOP HEAT PIPE

The design of a cryogenic loop heat pipe (CLHP) is presented in the paper. As the wick is required only in the evaporator section, very small pore size wicks can be used in applications with high thermal transport requirements and/or where the heat must be transported over a long distance against gravity. A FORTRAN program to solve the mathematical model and to determine the parameters for various boundary conditions has been developed. The CLHP is designed to transfer 5W heat at 70K using nitrogen or oxygen as working fluid. It will be a self priming type device which can operate against gravity with evaporator above the condenser as well as under microgravity condition. A G-M type single stage double inlet pulse tube refrigerator is coupled to the CLHP to test its performance. The mathematical model, design, fabrication integration of the heat pipe with the pulse tube system and testing with stainless steel wick at the evaporator will be described in the paper.

Development of pilot plant for cryogrinding of spices : A method for quality improvement

The development of a pilot plant for cryogrinding of spices is discussed in this paper. The unit has an indigenously designed and developed cryogenic screw cooler for optimal utilization of liquid nitrogen along with a digital signal processing system (DSP) for liquid nitrogen spray and automatic temperature control. In the first part, the advantages of cryogrinding over conventional grinding are described. The latter part discusses the details of the pilot plant, along with preliminary experimental studies using pepper as the sample. Experimental results clearly indicate the quality improvement of the cryoground spice in terms of increased volatile oil contents and flavour components.

LOX SEPARATION STUDIES USING CRYOGENIC VORTEX TUBE

In-flight collection of air, pre-cooling, liquefaction and separation of liquid oxygen (LOX) are key technologies for futuristic launch vehicles, Vortex tube technology is one of the few potential technologies for this application. Extensive studies have been carried out on straight and conical vortex tubes for developing vortex tube technology for high purity LOX separation. Studies show that 12mm. diameter conical vortex tube with L/D of 10 could achieve LOX purity of similar to 96% with separation efficiency of similar to 14% indicating that it is not possible to obtain both high LOX purity and high separation efficiency simultaneously in a single vortex tube. However, it is possible to achieve both high LOX purity and separation efficiency by staging of vortex tubes. LOX purity of 96% and separation efficiency of similar to 73.5% has been achieved for second stage vortex tube supplied with pre-cooled air having 60% oxygen purity. LOX purity has been further increased to 97% by applying controlled heating power over liquid oxygen flowing discharge surface of the vortex tube.

Experimental Studies of Convection in a Single Stage Pulse Tube Refrigerator

A single stage Pulse Tube Refrigerator has been designed, fabricated and operated with a 3kW GM type helium compressor with an indigenously developed rotary valve in the frequency range from 1.2 to 2.3Hz. The system produces a lowest temperature of 37.5K and a refrigeration power of 7.3W at 77K. The cold end temperature Tc of the Pulse Tube refrigerator depends on its orientation angle

Note: Development of a cryocooler based high efficiency cryosorption pump

\theta

Measurement of thermal conductivity of materials down to 4.5 K for development of cryosorption pumps

with respect to gravity vector and the increase in Tc arises due to the convection in the Pulse Tube. The lowest temperature occurs at

Indigenous development of a table top batch liquefaction for nitrogen using pulse tube crycooler

\theta = 0°

Simulation studies on the standing and traveling wave thermoacoustic prime movers

. The increase in Tc with change in

Studies of Adsorption Characteristics of Activated Carbons in between 4.5 to 10 K for Cryopump Applications

\theta

Numerical analysis on thermoacoustic prime movers for development of pulse tube cryocoolers

is small till about 70°. However, beyond this angle, Tc varies strongly and reaches a maximum value at